service on green line between -- >> nbc news, terrorism analyst evan coleman has worked extensively with the fbi in boston. let's bring him in on the phone. what are you hearing in material of injuries? >> some of these injuries, they don't look good. and i mean, that would suggest that these explosions, that they are the work of some kind of explosive device. it is something with some force. we've seen previous attempts by home grown extremists to bull their own bombs and it hasn't gone so well. an individual was trained by the taliban at a camp on the afghan/pakistani border debt made the a car bomb and later a number of experts would go on to laugh at how immaturish that was and how poor a design that was. this appears to be somewhat more sophisticated. and boston, unfortunately, i don't think is known as a great hub of violent extremists. there are a number of individuals in that area who have been picked up over the years on charges ranging from everything from terrorist financing to -- >> evan, i want to ask you. because nbc news has not confirm the nature of the explosion yet. is